As processor speeds continue to increase, memories providing data to the processor have become more and more of a bottleneck. In an effort to speed memory access, high speed caches were created to deliver data to processors. Generally, a cache only stores a fraction of the data stored in main memory. A cache “hit” occurs when the cache contains data the processor is requesting. A cache “miss” occurs when the cache does not contain data the processor is requesting. When a cache miss occurs, the data must be retrieved from main memory or disk. The time to fetch the data when a cache miss occurs, even from main memory, can be much greater than when a cache hit occurs. Increasing the percentage of cache hits and decreasing the number of cache misses, therefore, increases the overall performance of a computer system.
One approach to improving cache hits is to collect and analyze the data accesses of an executing program. A problem with this approach has been the amount of data accesses that an executing program generates even for a relatively short run time.